Means for processing dentures



Nov. 4, 1958 vs. MYERsoN MEANS FOR PROCESSING DENTURES Filed Oct. 27.1955 BY 2.( 4M;

MEANS FOR PROCESSING DENTURES I Simon Myerson, Waban, Mass.

Application October 27, 1953, Serial No. 388,494 1 Claim. (ci. 1st- 33)The present invention relates to a means for accurately reproducingoriginal models or trial dentures.

In the practice of prosthetic dentistry when preparing dentures, thedentist first prepares a trial plate consisting of wax or other similarcomponents in which various teeth are set in their proper positions.When this trial denture has been made and fitted to the mouth of thepatient and found satisfactory to esthetics, fit and articulation, it isthen subjected to a process hereinafter more fully described in which apermanent plastic material is substituted for the wax.

The reproduction of the trial wax denture into a permanent plasticdenture has llong been a recognized problem particularly with respect toproper articulation. In the ordinary process of producing a denture, thetrial dentures are attached by wax to a cast which is then placed inone-half of a container known as a flask, and after this portion of theinvestment has set, the top surface or land is painted with a film ofsoap or other separating medium to the edge of the trial denture whichprojects above the investment. The upper half of the flask is thensecured over the first mentioned half and a second section of plaster ispoured into the flask covering the trial denture. When this upper partof the investment has hardened, the flask containing the investment,cast and trial denture is placed in warm or hot Water until the wax hassoftened enough to be removed. The two halves of the investment therebyform a cavity mould already containing the artificial teeth in properposition in which a permanent plastic material, such as a resin ofmethyl methacrylate, is packed after first placing a thin sheet ofcellophane or the like over the cast.

Ordinarily much more plastic material is placed in the cavity than isneeded. The two halves of the investment are then fitted together andthe halves of the flask containing them are then forced together in apress device. As the two halves of the flask are forced together, excessplastic material will ooze out between the two opposite faces or landsof the investment. The flask is then removed from the press and excessplastic material is removed. This process, which is called trialpacking, is repeated several times until the operator believes justenough plastic material has been removed for the flask to completelyclose. Ordinarily he determines the ask is closed when he can no longerdetect plastic material being forced onto the land. This method ofdetermining whether the flask is properly closed is, however, inaccurateas the ask is not necessarily completely closed merely because there ,isno more plastic material being forced onto the land. In fact when trialpacking, the two halves of the ask do not ordinarily approximate eachother within .015 of an inch, as the acrylic resins which are used toform the denture tend not to ow through gaps of such narrow dimensions.vThe present invention overcomes these difliculties by providing amethod and equipment by means of which a technician forming a denturemay readily and properly close the t United StatesI Patent O PatentedNov. 4i, 1958 fit:

more accurately reproduced in the finished product than heretofore.Moreover, this considerable improvement in accuracy will be accompaniedby a substantial saving of time.

In this invention, I have provided a press for forcing the two halves ofthe flask together which has a measuring means which may be used todetermine accurately whether or not the ask is properly closed.

A further object and advantage of the present invention is that itenables the technician or operator to use efciently the plastic materialwhich forms the dentures, and to compensate for any known shrinkage orexpansion of this material while it is being used. In my method ofpreparing dentures, a trial denture is first formed and secured to acast and is then invested into one-half of the flask as is ordinarilydone. A melted layer of Wax, preferably very soft, is then painted ontothe land to a thickness of between .005 and .020 of an inch. The upperhalf of the flask is then placed in the correct position and in Contactwith the lower half, and plaster is poured into the second half of theflask, forming a ycomplete investment. The flask is then placed in ascrew press. The screw thereof is provided with a member which contactsthe upper member of the flask by means of which the ask members arepressed together.

In this invention, I provide a press having means for measuring theparticular position of the pressing member when the flask is properlyclosed. After noting or setting the particular reading on the measuringelement at which the two halves of the flask are held firmly together inposition, the flask is removed and opened. The wax is then removed inthe usual manner and the investment is painted with an alginate or atype of tin foil substitute. The denture resin is then packed in theordinary fashion into the cavity of the investment containing the teethwith more than enough material to form the denture. The flask is closedand placed in the press and the screw is turnedto force the two halvesof the ask together until the reading on the measuring device is thesame as it was previously. When the sections of the flask are forcedtogether, the excess denture resin is forced out of the investmentcavity into the space between the lands formed by the application of thesoft waX. This space is of the same magnitude as the thickness of thelayer of wax applied. The thickness of the space required between thelands will depend on the flowability of the particular resin being used,The denture is then cured in the usual manner.

One of the important merits -of the present invention is thepreservation of thev correct articulation of the artificial teeth asestablished lby the dentist. If the flask containing the denture has notbeen properly closed, the increased thickness of the denture in the areaof the posterior teeth will be increased, resulting in what is usuallytermed as opening of the bite.

These and other advantages and objects of the present invention will bemore fully understood when considered in connection with the drawings4in which:

Figure 1 is a plan view of a press containing a ask.

Figure 2 is a fragmentary sectional view of the measuring elements ofFigure. 1.

Figure 3 is a cross sectional view of the flask containing an investmentand denture.

Figure 4 is a fragmentary view of a modification of the elements ofFigure 2.

Referring to Figure l, there is shown a press embodying my invention inwhich an .accurate and full closure of the ask may beachieved ruring theprocessing of the denture. The press is provided with a base 1preferably flat, fixed to a frame 2. The frame 2 is provided with twoupwardly extending opposite legs 3 and 4 and a transverse span 5. Thespan 5 has acentrally located threaded hole 6 extending perpendicularlythrough it. This hole 6 may be provided at its upper end with aconcentric hardened steel bearing plate 7. Through this hole is threadeda crew -8 which is free to be moved .up and down. At the lower end ofthis screw Ais secured Va freely movable press element generallydesignated 9 which Acomprises an inner barrel 10 and an outer barrel 11,said barrel 11 having an outwardly extending circular base 12. Suitablysecured to this base is a plate 13 of hardened steel. The upper end ofthe screw is provided with a head 14 having ya hole through which a baror lever 15 is secured by a set screw 16. Instead of the rigid leverherein illustrated, a torque wrench lever capable of `being set to exerta pre-determined force may be employed.

A cylinder 17 having a central threaded aperture through it is fittedonto the screw 8 in a position at the upper end of the screw. Thiscylinder, although it is threaded on the screw 8, has sufliciently tighta fit so that it may not readily change its position relative to thescrew 8 unless intentionally turned. Normally it will turn with thescrew 8. In order to facilitate the moving of this cylinder whendesired, a marginal section 18 near the top of the side wall may beknurled. Also fitted on the screw is a nut 19 which is threaded to litonto the screw 8. At the upper end of this nut 19 is an annular upwardlyextending peripheral flange 20 which forms an inner recess 21 at thecenter of the nut. The upper edge 25 of this llange is beveled inwardlytowards the outer face of the cylinder 17.

The recess 21 has a sufliciently wide diameter as to permit the lowerend of the cylinder 17 to fit within it as the nut 19 and cylinder 17are screwed towards each other.

yOn the surface of the cylinder 17 is provided calibrations comprising aseries of horizontal parallel lines each at an equal distance apart,preferably J/10 of an inch apart. A vertical line divides thesehorizontal lines in equal sections. On the edge 25 of the nut 19 isprovided a series of twenty-five vertical equi-distant lines. -If thescrew 8 has ten threads to the inch, each calibration on nut 19 willindicate a relative change in the positions between cylinder 17 and nut19 of .004 of an inch. There may also be positioned on the screw 8 acase hardened locknut 22.

In the operation of this press after the trial denture 50 has beenplaced in `a flask 23 and with au investment 52 surrounding it, in themanner briefly mentioned above, with a layer of soft wax 53 separatingthe opposite lands 54 of the investment, the flask is then placed uponthe base 1 and the screw is turned down until the platey 13 comes intocontact with the top of the flask 23. The operator then tightens thescrew so that the edges of the two parts of the flask meet firmly asshown at 49, Figure 1. To properly position this flask each time, thebase 1 of the press m-ay be provided with a series of upwardly extendingpins 24 which may be used to center the flask at lall times. Havingclosed the flask firmly, the operator then turns the locknut 22 until itcomes into contact with the hardened bearing plate 7. He then screws thenut 19 downward until it contacts the locknut 22. He may take thereading at this point, or he may rotate the cylinder 17 downward untilit reaches a point at which the horizontal calibration marked zero onthe cylinder 17 registers with the zero on the upper edge of thecalibrated nut 19. This establishes the position at which the flask wasclosed. The screw 8 is then loosened and the flask is removed andopened. The wax forming the trial denture and the soft wax which wasplaced on the lower portion of the investment before the upper part ofthe investment was formed in then removed by boiling water or warmwater. If boiling water is used, the wax may be removed in about fourminutes, after which any remaining traces of wax are cleaned out byflushing.

The denture resin in a flowable state is then packed over the teeth andsurrounding cavity in the investment. Enough material is pressed intoposition to insure that when the lflask is closed there will be morethan enough resin to occupy the denture cavity. The flask is then closedand any excess resin will be squeezed out in a thin ribbon between thelands lof the two parts of the investment, which because of the coatingof soft wax placed there during the forming of this investment arespaced apart between .O05 and .020 of an inch. When the flask is thusforced into a closed position in the press, the operator can be certainthat the flask is properly closed if he turns the screw down to a pointat which the nut 19 comes into contact with the locknut 22 when thelocknut 22 is in contact with the bearing plate 7. This is the sameposition established by the original setting. `If the operator canrotate the nut 19 he will know the llask is still open. By means of themicrometer cylinder 17 and nut 19, he can determine to what extent it isopen and make correction accordingly. When the flask is closed, thedenture is cured and then removed from the investment; any excessplastic material in the form of a ribbon may then readily be removed.

In the modification .as illustrated in Figure 4, the screw 41 isthreaded through the bridge member 42 corresponding respectively to thescrew S and the bridge member 5 of Figure l. Secured to the bridgemember 42 is a bracket 43 supporting yan indicator device having a scalemember 44 and an indicator 45, pivoted at 46. The indicator has one endpositioned to point to the scale member 49 and the other end adapted tocontact the lower lsurface of the nut 47 whereby the longitudinalmovement' of the nut 47 may readily be registered 'on the scale Imember44.l

Alternatively, the indicator 45 may be used as an actuator for amicroswitch, which may be connected to a light circuit which will signalthe` closing of the flask.

Although I have illustrated my invention using screw pressure meansbecause this type of press is most commonly used, it is obvious that thepressing member may be operated `by a lever, air, or hydraulic pressure.Other modifications may be made without departing from this invention.

Having now described my invention, I claim:

A press for closing a dental flask comprising a base, a bridge memberarching over and supported from said base, said bridge member having athreaded hole ftherethrough, a screw threaded through said hole andextending downwardly toward said base, a plate supportedion the lowerend of the screw for closing a flask supported on the base, a nutthreaded on the screw above the bridge member and having a recess formedon its upper surface, a cylinder threaded on the screw above the 4nutand adapted to move in and out of the recess when the nut and cylinderare moved relative to one another on the screw, said nut and cylindereach being movable on the screw, and calibrations formed on the adjacentportions of the nut and the cylinder indicating relative positions ofthe nut and cylinder and the condition of the flask.

References Cited in the le of this patent UNITED STATES PATENTS1,424,383 Schleicher Aug. 1, 1922 1,941,780 Angell Jan. 2, 19342,006,903 Roelofs July 2, 1935 2,320,826 Mandel June 1, 1943 2,358,730Nelson et al. Sept .19, 1944 2,491,147 Zahn Dec. 13, 1949 2,666,263Laserson Jan. 19, 1954 2,761,175 Myerson Sept. 4, 1956 FOREIGN PATENTS46,874 Sweden Apr. 1, 1909 429,486 Germany May 29, 1926 1,045,870 FranceJuly 1, 1953

